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DARPA, the renowned bulgy-bonced battle-boffinry bureau (apparent motto: "If you can't beat them... well, some sort of murderous killer robot army would seem to be in order") has just issued its latest call for notions. This time, the Pentagon science chiefs want a new and ultra-puissant combo nightsight module.

This is because of the bewildering array of optics that well-equipped American troops nowadays find attached to their personal weapons (many of these things having been previously invented by DARPA). A fashionable combat soldier - or even a policeman, often enough - is these days offered a veritable panoply of shinies to fix alongside his gunbarrel.

There are "light intensifier" or starlight scopes, now many generations advanced from the early versions. These can pick up near-infrared light, which is fairly abundant at night compared to the visible wavelengths - outdoors, at least.

Then there are "thermal imagers", too, able to see longer-wavelength infrared which is given off by warm objects as opposed to super-hot ones such as stars, lightbulb filaments etc. Thermal imagers can see human bodies, hot vehicle engines and so on by their own emitted glow, rather than by light reflected off them as an eyeball or starlight scope does. Thermal imagers too have shrunk in size and complexity since they first appeared. (Older readers, like your correspondent, may recall the days when thermal imagers needed to be cooled to operate, and required top-ups of chiller gas as well as batteries.)

Then, quite apart from all this, there are ordinary visual aiming scopes often enough. These, like the other gunsights, need to have their aiming reticules "boresighted" - that is, accurately aligned with the gun barrel - every time they get attached to a weapon. (Movie scenes where people gaily snick aiming attachments on and off weapons and never bother to zero them on the range are strictly creative licence.)

Finally there are illuminators - gun lamps - giving out both visible and near-IR light. (You can also have a near-IR-only "black light"*, good for use with a starlight scope inside a building. It needn't involve anything more complex than an ordinary lamp with a filtering gel over the lens, to let through only the IR. In this way, enemies equipped only with eyeballs won't see your torchlight.)

At the moment, a soldier can use a long-wavelength thermal nightsight, or a near-IR starlight scope, or a visual scope for daylight conditions. But the thermal scope can't see gun-lamp illumination, and it can't see through glass* either. The starlight scope can't see body or engine heat, though the latest kinds are no longer crippled in daylight. The ordinary optical sight can't deal with darkness except by use of giveaway white light. Changing from one to another requires tiresome boresighting, or having an absurd number of appliances attached to one's weapon.

No more, say DARPA. The Pentagon boffins want a combo scope which can see by daylight, near-IR black light, and also view long-wavelength heat from people etc. The combo-scope would work with either white or black gun lighting, see through windows and everything - all in one. You wouldn't need to fiddle about changing systems and boresighting all the time.

You can read the full requirement from DARPA's Doctor Stu Horn here (pdf). ®

Bootnotes

*Long-wavelength IR from normally-hot objects can't get through glass. Only the shorter waves from hotter things - the sun, lightbulbs - can do this. That's why cars get hot on sunny days; the sunbeams get in and warm up the seats etc, but not to the red-hot point where the emitted radiant heat could get out of the windows again.

This is also why a firefighter with a thermal-imaging camera can spot fires through a window, even in a smoke-filled building - the fires being very hot - but not the living human bodies he may actually be trying to find.

**Yes, we know "black light" normally means ultraviolet, not infrared. Just to mix things up even worse, the special-ops community sometimes use UV as well, and have been known to call that black light too. To be fair, it does all look black to the naked eye. No matter. When you're a man in black aboard a black helicopter doing black ops using black funds against the black hats, different kinds of black lighting are merely shades of grey.